1. Field of the Invention
The invention relates to operators for movable barriers, such as rolling shutters, retractable awnings, gates, garage doors, overhead doors and the like, and more particularly to operators which can determine the absolute position of the barrier at all times, including after a power outage and subsequent manual relocation of the barrier.
2. Description of Related Art
One of the problems which must be addressed in designing and engineering operators for movable barriers is the provision of barrier position detection. Most electronic positioning systems used in barrier operators keep track of the barrier""s position by incrementing a position counter during one direction of travel and decrementing the position counter during the opposite direction of travel. This can cause errors if there are missed pulses or extraneous pulses during travel (such as from slippage of the barrier or motor).
Some barrier position detection systems employ a pass point. The pass point corresponds to a fixed location on the barrier, so that whenever the barrier moves past the pass point, the position detector is normalized or calibrated. By normalizing or zeroing out the position detector (or counter), the effects of missed pulses or slippage are eliminated. Some systems employ multiple pass points which provide further error removal capability. The pass point is a good solution in most situations, such as for garage door operators, which seldom move manually.
A more significant problem can occur in motorized awnings or rolling shutters. The rolling shutter assembly is frequently installed in a housing which is built into a wall. If power goes out on a rolling shutter system, the user will frequently move the rolling shutter manually to either open or close it. The power is off, but the gears of the positioning system move without power applied to assure manual override of an electric system for the purpose of power failures. Some users may also decide for convenience to move the shutter manually. When power returns, if the rolling shutter has been manually moved past all pass points, the operator, not encountering the pass point reference, may cause the rolling shutter to continue to move completely into the housing necessitating removal of the shutter from the housing. Removal of the rolling shutter from the housing frequently means removing a portion of an interior wall.
There is a need for a movable barrier operator with a position indicating system that provides the absolute position of the barrier, even after power outages or after the barrier has been moved manually. There is a need for a movable barrier operator which can unambiguously determine the position of the barrier after power is applied. There is a need for a movable barrier operator which can unambiguously determine the position of the barrier regardless of direction of travel.
A barrier operator position detector includes a first rotary member which is encoded to generate a first N bit subcode selected from N sequential bits of a M bit code word. The first N bit subcode has the property that every selected subcode of N sequential bits of the M bit code word has a unique value. N is greater than 1 and preferably 5. M is greater than N and preferably 32. A second rotary member is encoded to generate a second N bit subcode selected from N sequential bits of a Mxe2x88x921 bit code word, the second N bit subcode also has the property that every selected subcode of N sequential bits of the Mxe2x88x921 bit code word has a unique value (preferably Mxe2x88x921 is 31). A controller, responsive to the first subcode and the second subcode, generates a 2N bit multibit (or two N-bit subcodes) code. The 2N bit multibit subcode is representative of a unique position output, which can be decoded into a unique position of the barrier along its travel.
A movable barrier operator according to the invention includes an absolute position detector which provides a unique value for each position of the barrier along its path of travel. The absolute position detector employs two binary serial streams and one clock stream. After the first five cycles of the clock stream, the binary serial streams can be decoded by a microprocessor or other processor to produce an absolute position indication. Every clock edge produces a new absolute position value along the path of travel.
The absolute position detector employs three wheels; two data wheels and a clock wheel driven by a pinon. Each wheel rotates near a wheel state detector which produces digital signals comprising bit streams. Preferably an infrared emitter-sensor pair is used as the wheel state detector. However, any electromechanical system which produces a digital signal comprising bit streams, such as Hall sensors, laser discs, and so on, may be used. For convenience, the absolute position detector of the invention will be described in detail with reference only to the infrared emitter-sensor embodiment.
In the preferred embodiment, two of the wheels are data wheels or gears and have teeth distributed around their outer portions. One wheel has 32 teeth, the other wheel has 31 teeth. Each tooth of each data wheel has a corresponding data bit formed in the wheel before the tooth. Each data bit represents a single binary data bit. A space formed below a tooth represents a digital low; a solid area formed below the tooth represents a digital high. The 32 teeth wheel has a 32 bit binary stream formed in it. The stream is uniquely defined so that any consecutive 5 bits in the stream are different from any other consecutive 5 bits in the stream, including the rollover stream. The 31 teeth wheel is similarly defined, except the 31 teeth wheel has the same bit binary stream as the 32 bit wheel, with one bit missing.
Since the 32 teeth wheel and the 31 teeth wheel have different numbers of teeth and are driven by the same pinion, they rotate at different speeds. The pinion is driven externally by a gearing system that is driven by the motor. The motor can rotate clockwise or counterclockwise, so the pinion can also turn in both directions. Since the motor is bi-directional, an attached load comprising a barrier such as a door, awning, shutter or gate can move in either of two opposite directions. Preferably direction of travel information is obtained by storing the commanded direction of travel (e.g., the user commands the door to open by pushing the open button or to close by pushing a close button).
The movable barrier is operated through linear linkage of the load to the motor such as a trolley, or through rotational linkage to the motor, where the load is wound around the entire operator unit, such as in a rolling shutter. Since the two data wheels rotate at different speeds (because of the different number of teeth), the two binary streams have different repeat rates. This means that a given 5 bit stream from the 32 teeth wheel will not combine with the corresponding 5 bit stream from the 31 teeth wheel until 31 more revolutions of the 32 teeth wheel, or vice versa. In other words, a total of 31xc3x9732=992 unique two word values are possible without a rollover or repeated position concern. 992 unique positions is large enough to provide absolute position along a part of a movable barrier in most situations. An extra data wheel may be added for more positions (e.g., 32xc3x9731xc3x9730=29,760 positions). This mechanical linkage also means if the unit is moved manually, the 31 bit wheel and the 32 bit wheel will move, storing or representing for later reading by the controller, the position of the awning, door or shutter.
The third wheel is a clock wheel and is used to provide a clock signal for the position detecting system to enable proper sampling of the data wheel bit streams. The clock wheel includes 32 equally spaced openings. The clock wheel provides a digital low pulse signal when the center of a data bit on the 32 teeth wheel lines up with the center of a data bit on the 31 teeth wheel and when these centers are in line with the IR sensors. The clock signal is provided to the microprocessor which uses the clock signal as an interrupt to sample binary data from emitter-receiver pair associated with each data wheel. After the first 5 clock cycles, each data wheel has output a 5 digit binary stream, which when combined, gives 2 five digit binary numbers. This 5 digit binary number pair is decoded by the microprocessor which calculates an absolute position. Thereafter, every clock cycle triggers the sampling of a new binary digit from each wheel, the stored 5 bit binary number pair is updated, and a new absolute position of the barrier is determined.
The movable barrier operator according to the invention with absolute position detector (or encoder system) provides many advantages. It provides the absolute position of the barrier for every pulse edge of the clock signal from positioning gears turned by motor""s gearing system. Shortly after power is applied to the motor, the clock wheel would have produced 5 pulses. After 5 pulses, the encoder system determines the absolute position of the barrier. The encoder system can provide direction of travel after six pulses of the clock wheel. The encoder system discriminates false or unwanted pulses to prevent false positioning.
An absolute position is always provided shortly after power is applied (after 5 pulses and the first 5 digit binary pair is obtained), regardless of the stored value of the last position and regardless of where the barrier may have been moved manually. The absolute position detector also provides an opportunity for the system to do a validity check for every newly calculated position (e.g., by checking the absolute position between successive data streams, the direction of travel can be ascertained). It should also be noted that no presetting of the wheels prior to installation/operation is required.
Additional advantages and features of the invention may be appreciated from a perusal of the specification, including claims in light of the accompanying drawings.